Polyalkylene glycol-diorthosilicic acid ester lubricants and power transmitting fluids



United States Patent No Drawing. Filed July 8, 1965, Ser. No. 470,629Claims priority, application Germany, July 10, 1964,

20 Claims. of. 25249.6)

This invention relates to new and useful synthetic liquid compositionsor oils. More particularly, the invention is concerned with fluid or.oily compositions comprising a diorthosilicic acid ester or a mixturecontaining a diorthosilicic acid ester.

The fluid compositions of this invention may be used alone or admixedwith other liquid materialse.g., fluid bodies such aspolyoxyalkyleneglycol-diortho-silicic acidhexaalkyl esters disclosed inUS. Patent No. 2,776,307 as electrically insulating fluids, hydraulicfluids, damping fluids, lubricants, etc.

Synthetic lubricants, power transmission fluids, etc., must possess anumber of properties in order to be capable of heavy duty service undervarying operating conditions. Such fluids must be characterized by smallchanges in viscosity with temperature, remain fluid at low temperatures,be non-volatile at high temperatures, have high thermal and oxidativestability, and the lubricating films formed therefrom must have adequateload carrying capacities.

Silicic acid esters are known which more or less meet the aboverequirements, as, for instance, polyoxyalkyleneglycol-diorthosilicicacid-heXa-alkyl esters disclosed in U.S Patent No. 2,776,307. However,the viscosity indices of these esters' decrease in those instances wherethe esters have alkyl groups which contain more than 8 carbon atoms. Theesters having low viscosity indices are not satisfactory for applicationas jet propulsion engine oils.

-An object of the present invention is to provide silicic acid estershaving high boiling ranges, 10w volatilities, high viscosity indices,low viscos-ities at low temperatures and as well capable of forminglubricating films having satisfactory load carrying capacities.

Another object of this invention is to provide fluidcompositionssuitable for use as electrically insulating fluids,

been found that liquid material comprising diorthosilicic acid esters ofthe formula I i)z( )s n( R')n wherein A represents a polyoxyalkyleneradical having 1 3,335,227 Patented Aug. 15, 1967 "ice to 6 andpreferably 2 to 4 ether-oxygen atoms, R represents a polyoxyalkyleneglycol ether radical having 2 to 8 ether-oxygen atoms, R represents analkyl group having 9 to 20 carbon atoms, n is of the class consisting offrom 1 to 4 and 0 and wherein R and R may be the same or different,provides liquid or fluid compositions which are suitable for use aslubricants, brake fluids, hydraulic fluids, etc.

A preferred group of diorthosilicic acid esters for the purposes of theinvention has the following formulae:

are shown in the following table wherein a comparison of certain of theesters of the invention with certain known silicic acid esters havingsimilar molecular sizes has been set out. The known esters employed incomparison include diand tri-oxyalkyleneglycol-diorthosilicicacidheXa-isodecyl-ester (I, III) as well astri-oxyalkyleneglycol-diorthosilicic acid-hexa-iso-tridecyl-ester (VIII)corresponding to the formula:

The esters of the invention used in the comparison are the following:

(II) diethyleneglycol-di-o'rthosilicicacid-hexa-(diethyleneglycol-n-butyl-ether) -este r (VI)diethyleneglycol-di-orthosilicic acid-tri-(diethyleneglycol-ethyl-ether)-tridiethyleneglycol-n=butyl-ether)-ester (IV)triethyleneglycol-di-orthosilicicacid-heXa-(diethyleneglycol-n-butyl-ether) -ester (V)triethyleneglycol-di-orthosilicicacid-tri-(diethyleneglycol-ethyl-ether) -'tri-(diethyleneglycol-n-butyl-ether) ester (VII)triethyleneglycol-di-orthosilicicacid-tri-(diethyleneglycol-n-butyl-ether) -tri- (iso-decyl -ester (IX)triethylenegly-coldi-orthosilicicacid-tri-(diethyleneglycol-n-butyl-ether) -tri-(isotridecyl) -ester Theexpressions Oxo C H andOXoC H as used in the table designate radicals ofalcohols obtained from trimeror tetramer-propylene by hydroformylation(oxo synthesis) followed by hydrogenation of the hydroformylationproduct.

The load carrying capacity of the lubricating film of each of the esterswas determined using the four-ball testing apparatus as described byBoerlage (Lexikon der Schmiertechnik, G. Voegtle, Franckh'scheVerlangshandlun-g Stuttgart 1964).

In the table, two numbers are set out under the column Welding Value.The first number represents the highest possible load in kg. which thelubricating film withstands for one minute, without alteration, whilethe second number designates the load at which the balls are welded,i.e.,

4. inertness to broad temperatures changes is desirable or required.

frozen together. When the viscosity of an oil changes only slightly asTABLE I Di-orthosilicic acid esters Molec- Viscosity (st.) in C. Vls-Welding No. 71. ular cosity Pour value wt. index point, load, kg. A R R93.9 37.3 -40 54 o.

I omomocmom OX0-C1oH21.- 0 1,102 5.19 22.0 3,030 20,200 107 -09 100/170II CHCH 0CHzCHz p rr og og 1 4165 0 1,120 3.9 13.5 1,273 7,490 203 -71170/130 2 2 2 2 VI-- CH2CH2OCH2OH2 0 1,042 4.05 10.2 1,950 17,050 200 70130/190 111---- (CHZCH)2CHQCHL- 0 1,140 7.3 34.0 0,530 49,000 103 -03100/170 IV (CHzCHzO)2CHzCH2 (CHzCH20):-l1-C4H9 0 1,170 7.0 20.1 2,91513,050 130 -70 130/190 CH.CH.O .CH.CH..-.{ggggggggggggggg 0 1,030 0.3124.25 3.005 24,050 135 -09 130/190 VII (CHzCHaO)5CH9CHz(0H,o112o)rn-olH5 Oxo-C10Hz1 3 1,153 0.9 27.5 3,540 29,350 175 -05170/130 vrn (CHzCHzOhCHzCHn.-. OXO'CnHfl" 0 1,393 9.2 50.0 30,400 133-52 100/170 IX (CHgCHgO)zCHaCHz- (CHzCHzO) -n-C4H0 OXO-Cl3H27- 3 1,2343.93 41.3 11,400 100 -00 170/130 As can be seen from the table, theviscosities of silicic acid esters having approximately equal molecularweights I and II, III and IV, I and V, I and VI, III and VII, and VIIIand IX differ greatly. The viscosity indices of the esters II and IV(according to the invention) lie above 200, which is significantlyhigher than the viscosity index of the hexa-isodecyl-ester I. Theviscosity indices of the triethyleneglycol-diorthosilicic acid esters IVand V differ considerably from those of esters I and III, respectively,of comparable molecular size and, namely, by 17 or 18 units,respectively.

While the viscosity indices of hexa-alkyl esters decrease withincreasing size of carbon chains of the radicals R (III, VIII) highviscosity indices, i.e., above 180, for the silicic acid estersaccording to the invention are retained. If three of the six alkylradicals in the said silicic acid ester molecular are substituted bydiethyleneglycol-n-butyl-ether radicals (VII, IX), the viscosity indexis considerably improved.

The silicic acid esters according to the invention possess satisfactorylow temperature viscosities at, for example, -40 and at 54 C. Because ofthis favorable viscositytemperature relationship, the esters of theinvention are particularly well suited for use as lubricants, additivesto lubricants, as well as power transmission fluids, where extremely lowtemperatures must be encountered.

Although the esters IV and V, containing oxyalkyleneglycol etherresidues, are more viscous at 37.8 and 98.9 C. than the knownhexa-isodecyl-ester 1, they are much more fluid in the cold than thecommercially available lubricating oils of different chemicalcomposition used at present for gas turbine airplanes. The knownbis-(2-ethylhexyl)-sebacic acid ester, for instance, which has at 37.8C. the same viscosity as ester H, has a cold viscosity of 10,150 cst.

Ester VII, although highly viscous at 37.8 and 989 C., has substantiallythe same viscosity as ester I at extremely low temperatures. Thus, thedi-orthosilicic acid esters containing oxyalkyleneglycol-ether radicalsin their molecule according to the invention exhibit an unexpectedlygreat improvement in their viscosity-temperature relationship, their lowtemperature behavior, as well as an increased load carrying capacity oftheir lubricating films as compared with the di-orthosilicic acid estersknown in the art.

Because of the high load carrying capacity of lubricating film, theesters according to the invention have proved especially useful underthe application of high loads of the resulting mixed friction.

Polyoxyalkyleneglycol-diorthosilicic acid-hexaoxyalkylene-ether estersaccording to the invention have molecular weights below 900 and areespecially suitable for use as hydraulic fluids due to their highviscosity indices, their low viscosities at low temperatures andadequate viscosities at high temperatures, i.e., under conditionswherein a function of the temperature, it likewise exhibits but anextremely small pressure responsivity. This property is of considerableimportance for hydraulic fluids. For instance, diethyleneglycol-diorthosilicic acid-hexa-(ethyleneglycol-n-butyl-ether)-ester(molecular weight 862) has a viscosity index of 218. Its viscosity at-40 and 54 C. amounts to 780 and 3460 cst., respectively, whichconstitute very low values. Its viscosity at 988 C. amounts to 4.1 cst.,which is considerably higher than that of the dibasic carboxylic acidesters known in the art.

The esters of this invention can be used alone or in admixture withother liquid materials known in the art as lubricants or powertransmission fluids, e.g., mineral lubricants, dicarboxylic acid esters,phosphoric acid esters, organo-silicium compounds of differentstructure, as well as with conventional oxidation inhibitors and otherlike conventional additives. For instance, they may be admixed with (1)a liquid dicarboxylic acid ester or with (2) a liquid organo-siliciumcompound, as, for example, a methyl polysiloxane, or (3) with both aphosphoric acid ester and an oxidation inhibitor. The ester of theinvention is present in any admixture in an amount equal to at least 5%,preferably at least 50%, of the resulting admixture.

An especially well suited oxidation inhibitor is phenothiazine. It canbe added in amounts from 0.1 up to 1.5% by weight, dependant upon thequantity of the lubricant.

Conventional additives for improving the oiliness of the lubricantsconsisting of or containing the esters of the invention, as for instancetricresylphosphate may be added in amounts from 0.1 up to 3% by weightdependant upon the quantity of the lubricant. It is not howevernecessary to employ these additives, since the esters according to theinvention per se exhibit outstanding lubricating action.

The diorthosilicic acid esters can be prepared, for instance, byreacting stoichiometric mixtures of suitable alcohols and ether alcoholswith gaseous SiCl according to the disclosure of German Patent No.1,142,855 or as disclosed in German patent application R 32,696 IVb/120, Deutsche Auslegeschrift 1,180,359.

The following examples are intended to illustrate the invention and arenot to be interpreted as limiting the same.

Example I A reaction vessel (a so-called bubble-column reactor)consisting of a vertical glass tube with an internal diameter of 69 mm.and a height of 550 mm. provided with a glass frit (Jena apparatusglass, grain coarseness 2) in its bottom was charged with 121 g.diethyleneglycol and 1122 g. diethyleneglycol-n-butylether, which hadpreviously been dried to a water content below 0.1%. Siliciumtetrachloride was applied dropwise from a dosing vessel 5 into anevaporator coil heated at C., which was gastight connected with the saidreaction vessel, by a conduit joining the said reaction vessel below thesaid glass hit. The silicium tetrachloride vapors evolved in theevaporator coil were sucked through the frit under a vacuum of oftheinvention to the conventional ester lubricant are shown in thefollowing Table 2, wherein the properties of the two single esters areshown in comparison with those of the ester mixture, hereinafterdesignated admixture 180 torr. The ascending SiCl vapors together withthe 5 50/50 percent by vol.

TABLE 2 Viscosity in est. at 0. Welding Viscosity Flame value load d4index point, C. in kg.

Bis-3,5,5-trimethy1hexyl adipate 0. 916 3.15 11.86 15,720 147 222150/160 Diethyleneglycol-diorthosilicic acid-tri-(diethyleneglycol-n-butylether)-tri- (isodecyD-ester 0- 969 3- 9 14. 4310, 100 188 264 170/180 Admixture, 50/50 percent by vol 0. 944 3. 5213.01 12, 700 169 238 170/180 hydrogen chloride evolved during thereaction formed a Example 3 bubble-column of 420 mm.'height with theliquid in the reactor. The liquid mixture of said alcohol and ether,

70 parts by volume bis-3,5,5-(trimethylhexyl)-adipate were admixed withparts by volume diethyleneglycoldiorthosilicic acidhexa-(diethyleneglycol-n-butylether)- ester (ester II as hereinbeforementioned). The properties of the two single esters are shown incomparison with those of the ester mixture, designated admixture 70/ 30%by course of the reaction. 357 g. SiCl, were introduced and 25 vol. inTable 3.

TABLE 3 Viscosity in cst. at C. Weldin Viscosity Flame value load (14index point, C. in kg.

Bis-3,5,5-(trimethylhexyD-adipate. 0.916 3. 15 11. 86 15, 720 147 222150/160 Ester II 035 3.9 13.5 7, 490 204 251 170/1s0 Admixture, 70/30percent by vol 0. 952 3. 4 12. 69 11, 150 163 230 170/180 convertedduring 100 minutes. After termination of the reaction, the reactionvessel was heated at 110 C. for 2 hours whereby dissolved hydrogenchloride was removed from the reaction mixture under introduction ofnitrogen at a vacuum of 20 torr. (After the said treatment theBeilstein-reaction was negative.) Thereafter the non-reacted excessamounts of the reactants (125 g.) were distilled off from the reactionproduct under a vacuum of 0.01 torr up to a temperature of 196? C. Asdistillation residue 1150 g. of diethyleneglycol-diorthosilicic acidhexa (diethyleneglycol n butylether)ester (density d =1.038, index ofrefraction n =l.4452) were obtained. The silicium content of the productester was determined to 5.02% (calculated 4.98%); the viscosity of theester at 989 C. was 3.9 cst., at 37.8 C. 13.5 cst., at 40C. 1273 cst.,at 54 C. 7490 est; its viscosity index amounted to 203, its flow point(or setting point) was 71 C.

In analogous manner other esters according to the invention can beprepared.

Due to the admixture of the ester of the invention the followingpropertiesof dibasic esters, serving as lubricants for turbo-jets aregenerally improved:

The viscosity in the temperature range above 50 C. is increased, in thetemperature range below 37.8 C. decreased. The viscosity index isincreased, the flame point and the load carrying capacity are alsoincreased.

Example 4 75 parts by volume of a mineral lubricating oil (free of anyadditive) were admixed with 25 parts by volume of 1diethyleneglycol-diorthosilicic"acid-hexa-(diethyleneglycoln-butylether)-ester(ester II of the invention). A comparison of the lubricant so obtained(hereinafter called admixture 75/25 percent by vol.'M) with the saidmineral oil and ester II has been set out in Table 4.

Example 5 TAB LE 4 Viscosity in cst. at C.

. v Viscosity Flame Setting d4 index point, C. point, O.

Mineral lubricating oil 0.990 11. 5 130 25, 79 238 19 Ester II 1. 035 3.9 13. 5 132 204 251 72 Admixture, 75/25 percent by vol. M 1. 002 9.0167. 6 4, 030 241 -21 Diethyleneglycol-diorthosilicic acid-tri-(diethyleneglycol-n-butylether)-tri- (isodecyl)-ester 0. 969 3. 9 14. 43152 188 252 71 Admixture, 50/50 percent by vol. M 0. 979 6. 4 34. 7 2,136 244 23 The admixture according to Examples 4 and 5 represent motoroils, which meet the demands for several classes according to theSAE-classification (Society of Automotive Engineers).

Due to the addition of the esters of the invention to minerallubricating oils, essential properties of these oils are improved. Theviscosity index is increased (as for instance for 36 units at anaddition of 25% of the ester of the invention). The viscosity,especially at low temperatures is diminished. The flame points areraised and the setting points are lowered. Further on, the lubricatingaction is improved.

We claim:

1. A lubricant and power transmission fluid comprising at least 5% byweight of a diorthosilicic acid ester of the formula:

wherein A represents a polyoxyalkylene radical having 1 to 6 etheroxygen atoms, R represents a polyoxyalkylene-glycol-ether radical having2 to 8 ether-oxygen atoms, R' represents alkyl having 9 to 20 carbonsatoms, and n is of the class consisting of integers of from 1 to 4 and 0admixed with another liquid lubricant.

2. A lubricant and power transmission fluid according to claim 1additionally containing an anti-oxidant.

3. A lubricant and power transmission fluid according to claim 1 whereinsaid diorthosilicic acid ester is RO liOAOSlOR wherein R is as definedin claim 1, and A is a polyoxyalkylene radical having 1 to 6 etheroxygen atoms.

4. A lubricant and power transmission fluid according to claim 1,wherein said diorthosilicic acid ester has the formula:

wherein A, R, and R are as defined in claim 1.

5. A lubricant and power transmission fluid according to claim 1,wherein said diorthosilicic acid ester is diethylenegylcoldiorthosilicic acid hexa-(diethyleneglycol-nbutyl-ether)-ester.

6. A lubricant and power transmission fluid according to claim 1,wherein said diorthosilicic acid ester is diethyleneglycoldiorthosilicic acidtri-(diethyleneglycolethyl-ether)-tri-(diethyleneglycol-n-butyl-ether)ester.

7. A lubricant and power transmission fluid according to claim 1,wherein said diorthosilicic acid ester istriethyleneglycol-diorthosilicicacid-hexa-(diethyleneglycoln-butyl-ether) -ester.

8. A lubricant and power transmission fluid according to claim 1,wherein said diorthosilicic acid ester is triethyleneglycoldiorthosilicic acid tri-(diethyleneglycolethyl-ether) -tri-(diethyleneglycol-n-butyl-ether) -ester.

9. A lubricant and power transmission fluid according to claim 1,wherein said diorthosilicic acid ester is triethyleneglycoldiorthosilicic acid-tri-,(diethyleneglycol-n butyl-ether) -tri-(iso-decyl) -ester.

10. A lubricant and power transmission fluid according to claim 1,wherein said diorthosilicic acid ester istriethyleneglycol-diorthosilicicacid-tri-(diethyleneglycoln-butyl-ether) -tri- (iso-tridecyl -ester.

11. A lubricant and power transmission fluid comprising at least 5.0% byweight of a diorthosilicic acid ester of the formula:

R R 6 6 ROQlOAOS lOR wherein A and R are as defined in claim 11.

14. A lubricant and power transmission fluid according to claim 11,wherein said diorthosilicic acid ester has the formula:

wherein A, R and R are as defined in claim 11.

15. A lubricant and power transmission fluid according to claim 11,wherein said diorthosilicic acid ester is diethyleneglycoldiorthosilicic acid hexa-(diethyleneglycol-n-butyl-ether) -ester.

16. A lubricant and power transmission fluid according to claim 11,wherein said diorthosilicic acid ester is diethyleneglycoldiorthosilicic acid tri (diethyleneglycolethyl-ether)-tri-(diethyleneglycol-n-butyl-ether)- ester.

17. A lubricant and power transmission fluid according to claim 11,wherein said diorthosilicic acid ester is triethyleneglycoldiorthosilicic acid hexa (diethyleneglycol-n-butyl-ether -ester.

18. A lubricant and power transmission fluid according to claim 11,wherein said diorthosilicic acid ester is triethyleneglycoldiorthosilicic acid tri (diethyleneglycolethyl-ether)-tri-(diethyleneglycol-n-butyl-ether)- ester.

19. A lubricant and power transmission fluid according to claim 11,wherein said diorthosilicic acid ester is triethyleneglycoldiorthosilicic acid tri(diethyleneglycol-n-butyl-ether)-t1i-(iso-decyl)-ester.

20. A lubricant and power transmission fluid according to claim 11,wherein said diorthosilicic acid ester is triethyleneglycoldiorthosilicic acid tri(diethyleneglycol-n-butyLether)-tri-(iso-tridecyl)-ester.

References Cited UNITED STATES PATENTS 2,724,698 11/ 1955 Kittleson25249.6 2,947,772 8/1960 Eynon 25249.6 X 3,029,269 4/1962 Abbott 25249.6X 3,118,841 1/1964 Moreton 25249.6 X 3,133,111 5/1964 Wheeler 25249.6 X

DANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,336,227 August 15 1967 Herbert G'othel et a1. It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Columns 5 and 6 TABLE 2 third column, line 3 thereof, for "d 52" read 353 column 8 line 27 for "((501) (OR) (OR) "read A(OSi) (OR) (OR Signedand sealed this 15th day of October 1968 (SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr. Attesting Officer Commissionerof Patents

1. A LUBRICANT AND POWER TRANSMISSION FLUID COMPRISING AT LEAST 5% BYWEIGHT OF A DIORTHOSILICIC ACID ESTER OF THE FORMULA: